The present invention relates generally to electrodynamic machines and, more particularly, to methods and apparatus for making armatures for such machines by forming and inserting a plurality of single-turn hairpin conductors into peripheral slots of an armature core and securing the free distal ends of the hairpin conductors in a commutator which is pressed onto the armature core.
In the manufacture of armatures for electric motors used for example in golf carts, lift trucks and similar applications, a stack of armature laminations are pressed onto an armature shaft to form an armature core. The laminations have circumferentially spaced openings adjacent or extending to their edges which openings are substantially aligned as the laminations are stacked to define a plurality of radially extending slots around the periphery of the core. Rectangular wire is formed into single-turn coils taking the form of loops, commonly called hairpins, for insertion into the armature core slots. Prior to insertion, the hairpin conductors are shaped such that the legs of the hairpin conductors are spread and oriented to be inserted into different slots of the armature core. After shaping, the hairpin conductors are often referred to as frog legs.
To facilitate assembly of armatures, particularly hand assembly, the slots are open, i.e. extend to the edges of the laminations, and are made sufficiently wide that the hairpin conductors can be moved into the open slots from the cylindrical side face of the core. However, for such wide open slots, insulating wedges are also fitted into the slots or other arrangements are made to retain the hairpins within the slots during rotation of the armature. One hairpin retaining arrangement is to make the slots closed or with only a narrow opening at the edges of the laminations. If the slots are closed or have openings which are not as wide as a hairpin conductor, the hairpin conductors must be inserted into the armature core from the ends of the core.
The free ends of the hairpin conductors emerging from the opposite end of the armature core are also spread and oriented to be received within risers or other conductor receiving structure of a commutator. Finally, a commutator is pressed onto the armature shaft engaging the free ends of the hairpin conductors which are ultimately brazed, welded or otherwise secured to the commutator.
In an effort to automate the manufacture of electric motors, a number of systems have been developed to perform one or more of the noted operations required to produce an armature. For example, U.S. Pat. No. 1,555,931 discloses assembly of an armature wherein an armature core is initially formed and hairpin conductors are preformed into frog legs. The frog leg conductors are manually inserted into an armature core and then simultaneously driven through the armature core by a press.
U.S. Pat. No. 1,544,623, which was reissued as Re. 16,823, discloses a machine for receiving an armature core having frog leg conductors already inserted therein, holding slot insulators in place while forcing the conductors through the core, and bending the ends of the conductors which extend beyond the core to predetermined positions.
U.S. Pat. No. 1,661,344 discloses armature assembling apparatus wherein frog leg conductors are initially partially inserted into slots of an armature core which is then loaded into the assembling apparatus. A cylinder is operated to force all conductors through the core in one operation.
U.S. Pat. No. 1,556,893 discloses apparatus for making armatures wherein a commutator is press fitted onto an otherwise completed armature core. Cam operated slides force free ends of hairpin conductors extending through the armature core inwardly to be received within a commutator.
U.S. Pat. No. 1,556,892 discloses apparatus for making armatures wherein cam driven slides clamp deformable riser tangs on a commutator to simultaneously connect all commutator bars to armature conductors.
U.S. Pat. No. 1,556,891 discloses apparatus for simultaneously twisting the ends of hairpin conductors already inserted into an armature core to align them with commutator bars. Cam inserted forming members ensure that the bending does not materially weaken hairpin insulation.
U.S. Pat. No. 1,690,336 discloses apparatus for bending the ends of hairpin conductors already inserted into an armature core.
U.S. Pat. No. 1,703,188 discloses a machine for receiving an armature core with hairpins inserted therein and for bending the ends of the hairpins toward a central armature shaft prior to bending the hairpins for alignment with commutator bars.
U.S. Pat. No. 4,437,230 discloses preliminarily bending ends of hairpin windings in an armature core such that a layer of insulation is not required between terminal portions which extend between the armature core and a commutator.
U.S. Pat. No. 4,207,669 discloses a partially automated system which begins with coiled wire and produces an armature core ready to receive a commutator. Wire is formed into hairpin loops which are individually inserted into a retaining mechanism. Once fully loaded, the mechanism is transported to a working zone where the mechanism is operated to form a set of coils. The mechanism containing the coils is conveyed to a table where it is manually oriented and the table is moved toward a head which removes the coils from the mechanism. The empty mechanism is returned for reuse. The head next inserts the coils into slots an armature core which is manually installed into a receiver as the coils are being removed from the mechanism. The armature cores are then manually installed in a storing station. The armature cores are fed into a mechanism for pressing the coils into the armature core. The ends of the coils are then moved apart from one another by operation of the mechanism.
In spite of these substantial efforts, armatures for electric motors are still commonly hand assembled resulting in high expense and product inconsistencies which are characteristic of hand assembly. Thus, a need remains for methods and apparatus for automating the manufacture of armatures for electrodynamic machines by mechanically combining a plurality of single-turn hairpin conductors with an armature core and a commutator to form inexpensively and consistently such armatures without manual assembly.